Department of Biology, University of Turku, Turku, Finland.
Oecologia. 2011 Feb;165(2):277-87. doi: 10.1007/s00442-010-1772-4. Epub 2010 Sep 17.
Carotenoids in the egg yolks of birds are considered to be important antioxidants and immune stimulants during the rapid growth of embryos. Yolk carotenoid composition is strongly affected by the carotenoid composition of the female's diet at the time of egg formation. Spatial and temporal differences in carotenoid availability may thus be reflected in yolk concentrations. To assess whether yolk carotenoid concentrations or carotenoid profiles show any large-scale geographical trends or differences among habitats, we collected yolk samples from 16 European populations of the pied flycatcher, Ficedula hypoleuca. We found that the concentrations and proportions of lutein and some other xanthophylls in the egg yolks decreased from Central Europe northwards. The most southern population (which is also the one found at the highest altitude) also showed relatively low carotenoid levels. Concentrations of β-carotene and zeaxanthin did not show any obvious geographical gradients. Egg yolks also contained proportionally more lutein and other xanthophylls in deciduous than in mixed or coniferous habitats. We suggest that latitudinal gradients in lutein and xanthophylls reflect the lower availability of lutein-rich food items in the northern F. hypoleuca populations and in montane southern populations, which start egg-laying earlier relative to tree phenology than the Central European populations. Similarly, among-habitat variation is likely to reflect the better availability of lutein-rich food in deciduous forests. Our study is the first to indicate that the concentration and profile of yolk carotenoids may show large-scale spatial variation among populations in different parts of the species' geographical range. Further studies are needed to test the fitness effects of this geographical variation.
鸟类蛋黄中的类胡萝卜素被认为是胚胎快速生长过程中的重要抗氧化剂和免疫刺激剂。蛋黄中类胡萝卜素的组成受母鸟在产卵时饮食中类胡萝卜素组成的强烈影响。因此，类胡萝卜素的空间和时间可用性差异可能反映在蛋黄浓度中。为了评估蛋黄类胡萝卜素浓度或类胡萝卜素特征是否存在大尺度的地理趋势或在不同栖息地之间存在差异，我们从 16 个欧洲 pied flycatcher（Ficedula hypoleuca）种群中收集了蛋黄样本。我们发现，蛋黄中叶黄素和一些其他叶黄素的浓度和比例从中欧向北逐渐降低。最南端的种群（也是发现于最高海拔的种群）也显示出相对较低的类胡萝卜素水平。β-胡萝卜素和玉米黄质的浓度没有表现出任何明显的地理梯度。蛋黄在落叶林中也比在混合林或针叶林中含有更多的叶黄素和其他类胡萝卜素。我们认为，叶黄素和类胡萝卜素的纬度梯度反映了在北部 F. hypoleuca 种群和山区南部种群中，富含叶黄素的食物供应较低，这些种群相对于树木物候开始产卵的时间比中欧种群更早。同样，栖息地间的变异可能反映了在落叶林中叶黄素丰富的食物更容易获得。我们的研究首次表明，蛋黄类胡萝卜素的浓度和特征可能在物种地理分布范围内不同种群之间表现出大规模的空间变化。需要进一步的研究来测试这种地理变化对适应性的影响。
